Rosberg fastest in rainy Sao Paulo

Persistent rain emerged the victor on Formula One's final Friday practice session of the season, with Mercedes' Nico Rosberg quickest thanks to his time set early in the day.

Rosberg's lap of one minute 24.781secs - around an Interlagos circuit regarded as one of the finest in the world - was posted when the conditions were at their optimum, and even then that was a damp track.

Compare that to the best practice time of 1:13.188secs of a year ago from eventual race winner Jenson Button in his McLaren and it offers up an idea as to the stark difference in settings.

Throughout the opening 90 minutes the conditions ensured that even come the closing 20 minutes, when the rain finally relented, the track was still wet enough that Rosberg's time would not be beaten.

Team-mate Lewis Hamilton finished within half a second, and Sebastian Vettel was six tenths of a second adrift.

It would appear the rain is the only factor that could scupper the 26-year-old's bid to equal a further two records on Sunday.

Vettel can match the 60-year-old mark of nine consecutive victories set by Alberto Ascari, along with Michael Schumacher's 2004 haul of 13 wins in one season.

However, the forecast for Saturday and Sunday makes for grim reading, which will at least offer up the prospect of a thriller to conclude the campaign following Vettel's recent run of dominance.

So far this season there has yet to be a wet race, but that is poised to change and allow F1 to potentially sign off for 2013 in style.

With the leading times in FP1 set on the intermediate wet-weather tyres, further rain throughout the afternoon resulted in the drivers switching to full wets in FP2 to cope with the worsening conditions.

At one stage, with 40 minutes remaining, 12 of the 22 drivers had not set foot outside the garage, although that scenario changed over the closing stages.

Up until six minutes from the end Rosberg was again in front, only to be toppled by Vettel by seven tenths of a second.

Rosberg, however, had the final say, going top 40 seconds from the end with a lap of 1:27.306, albeit just over 2.5secs slower than his best from from FP1.

Vettel had to content himself with second on the timesheet, a quarter of a second down, followed by Red Bull team-mate Mark Webber, due to start his 215th and final F1 race on Sunday before heading off to compete in sportscars with Porsche.

Lotus' Heikki Kovalainen, completing the second of a two-race deal as replacement for Kimi Raikkonen who underwent back surgery last week, was a fine fourth, 0.823secs back, followed by Lewis Hamilton in his Mercedes.

At one stage Hamilton pirouetted through 360 degrees, but was able to control the spin before rejoining the circuit.

Behind Toro Rosso's Jean-Eric Vergne in sixth, Felipe Massa - on his final outing after eight years with Ferrari - was 1.234secs adrift in seventh, with team-mate Fernando Alonso 11th.

Overall, the spread of times across the 22 drivers was 4.464secs, with Button winding up at the back of the field.